Human beings are believed to have a number of brainwave states that correspond to specific frequency ranges. The “delta” brainwave state, corresponding to a frequency range of up to about 3 or 4 Hz, is associated with deep sleep and deep relaxation. The “theta” brainwave state, corresponding to a frequency range from about 3 or 4 Hz to about 7 or 8 Hz, is associated with drowsiness, dreaming sleep, daydreaming and creativity, and the “alpha” brainwave state, corresponding to a frequency range from about 7 or 8 Hz to about 12 or 13 Hz, is associated with awake relaxation and meditation. The “beta” brainwave state, corresponding to a frequency range from about 12 or 13 Hz to about 30 Hz, is considered a normal, fully alert state, typically associated with thinking and concentration. The “gamma” brainwave state begins above about 30 Hz.
It is believed that human brainwave frequencies can synchronize with external stimuli at particular frequencies. This process is referred to as brainwave entrainment. Thus, it is believed that exposure to audio or visual stimuli at a frequency corresponding to a given human brainwave state can facilitate a human brain entering the brainwave state associated with that frequency.
One notable example of a device designed for facilitating entry into a desired human brainwave state is the flickering lamp developed by artist Brion Gysin and mathematician Ian Sommerville and known as the “dreamachine”. The “dreamachine” was constructed by forming a hollow cylinder having equally spaced apertures defined therein, supporting the cylinder on a turntable such as a record player, and suspending a light bulb inside the cylinder. Because of the rotation of the cylinder, light emitted from the apertures would produce a flickering effect for a stationary observer, and the rotation speed and aperture spacing of the “dreamachine” were selected to generate a flicker frequency between about 7 or 8 Hz and about 12 or 13 Hz, corresponding to the alpha brainwave state. It is believed that a user can be guided into an alpha brainwave state by sitting close to the “dreamachine” and “viewing” the rotating cylinder with the user's eyes closed.
Other techniques for attempting brainwave entrainment use electronically controlled flickering light sources, sometimes in conjunction with audio stimuli (i.e. “binaural beats”) at the same frequency range, in an effort to selectably facilitate entry into a desired human brainwave state. For example, recordings may produce the visual stimuli at particular frequencies when played back on a television or computer monitor, or electronically controlled light sources such as light-emitting diodes (LEDs) producing pulses at specific frequencies can be integrated into goggles.